Surgical blade assembly including a static guide bar and an oscillating blade

ABSTRACT

A blade assembly for use with a surgical saw. The blade assembly may comprise a static guide bar, a blade and a drive member, that when actuated, oscillates the blade. The blade may further comprise teeth that extend distally from the static guide bar, the teeth adapted to form a kerf in tissue against which the teeth are pressed. The static guide bar may be dimensioned to fit into the kerf formed in the tissue cut by the teeth. The static guide bar may comprise a thickness dependent on a length of the static guide bar. The blade assembly may be configured such that blade may be the only oscillating component of the blade assembly to provide a generally constant mass moment of inertia irrespective of the mass and/or length of the static guide bar.

RELATIONSHIP APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/814,151, filed 15 Nov. 2017. U.S. patent application Ser. No.15/814,151 is a continuation of U.S. patent application Ser. No.15/418,122, filed 27 Jan. 2017. Application Ser. No. 15/418,122 is adivisional of U.S. patent application Ser. No. 14/751,397, filed 26 Jun.2015, now U.S. Pat. No. 9,554,808. Application. Ser. No. 14/751,397 is adivisional of U.S. patent application Ser. No. 14/191,576, filed 27 Feb.2014, now U.S. Pat. No. 9,072,526. Application Ser. No. 14/191,576 is adivisional of U.S. patent application Ser. No. 13/777,236, filed 26 Feb.2013, now U.S. Pat. No. 8,702,710. Application Ser. No. 13/777,236 is adivisional of U.S. patent application Ser. No. 13/102,382, filed 6 May2011, now U.S. Pat. No. 8,403,932. Application Ser. No. 13/102,382 is adivisional of U.S. patent application Ser. No. 12/334,886, filed 15 Dec.2008, now U.S. Pat. No. 8,043,292. Application Ser. No. 12/334,886 is adivisional of U.S. patent application Ser. No. 10/887,642, filed 9 Jul.2004, now U.S. Pat. No. 7,497,860. The contents of the applications fromwhich this application claims priority are explicitly incorporatedherein by reference in their entirety.

BACKGROUND OF THE INVENTION

A sagittal saw is a powered surgical tool that is often used in anorthopedic surgical procedure. A sagittal saw generally includes ahandpiece that houses a motor and the complementary control circuit thatregulates the actuation of the motor. Extending forward, distally, fromthe handpiece, is a planar saw blade. The most forward end of the sawblade is formed with teeth for cutting hard tissue against which theblade is applied. A drive mechanism internal to the housing transfersthe power developed by the motor to the blade. More particularly, thedrive mechanism converts the rotary motion produced by the output shaftof the motor to the blade so that the blade moves in an oscillatory,back-and-forth pattern in the plane in which the blade is aligned.Consequently, when a sagittal saw is actuated, the blade teeth move in aback-and-forth pattern against the hard tissue or bone to which theteeth are applied. As a consequence of this motion and the forwardpressure applied by the surgeon holding the saw, the teeth cut andseparate the hard tissue or bone.

A sagittal saw is often used in an orthopedic surgical procedure toselectively remove bone. One particular type of orthopedic surgicalprocedure in which the saw is used is a joint replacement procedure. Asthe name implies, in this type of procedure, the surgeon resects thebone between the joints in the patient and substitutes an artificialjoint.

In orthopedic surgical procedures, it is very important to ensure that,when a bone section is separated from the rest of the bone, the sectionis removed along very precise cut lines. This is very important in ajoint replacement procedure because the substitute joint typically has acomponent that is designed to precisely fit in the space defined by cutlines of the section of bone that is left in place.

Recently, there has been proposed a new type of surgical sagittal sawthat does not include a flat oscillating blade. This saw insteadincludes an endless metal band that is formed with outwardly directedteeth. The band is wrapped around a static guide that extends forwardfrom the handpiece, with the band teeth extending outwardly from theguide. A drive mechanism rotates the band. Since the guide of theproposed saw does not move, it is believed that many of the problemsassociated with saws that have oscillating blades would be eliminated.One example of this type of saw is disclosed in U.S. Pat. No. 5,725,530.

However, there are disadvantages associated with the above saw. It isexpensive to provide the toothed metal band. Also, the metal bandappears prone to fatigue and, consequently, breakage. The time it takesto replace this metal band while in the middle of a surgical procedurecan appreciably increase the overall time required to perform theprocedure.

Moreover, one of the goals of modern surgery is to, whenever possible,perform the procedure using a minimally invasive surgical (MIS)practice. As the name implies, in an MIS procedure only a relativelysmall incision is made with minimal soft tissue disruption in order togain access to the surgical site. Minimizing the extent to which apatient's tissue is exposed reduces the amount of tissue that is exposedto the ambient environment and the potential for infection caused bysuch exposure. Furthermore, reducing the extent to which the patient'stissue is incised minimizes the amount of tissue that then needs toheal.

In order to perform a minimally invasive surgical procedure on a bone orbone joint, only a relatively small portion of the surrounding softtissue is incised to expose the bone or the joint. Consequently, thebone or joint is not well exposed. In order to make the resection in thebone, the oscillating saw blade that is employed is typically longerthan the saw blade used to perform a conventional, resection surgicalprocedure. Given the relatively long length of the blade, the blade hasa mass moment of inertia that is appreciably greater than the massmoment of inertia associated with shorter-length blades. Consequently,when the saw to which this blade is attached is actuated, more vibratorymotion is created by the blade and transferred to the rest of thehandpiece than when a shorter blade is used. This increased vibratorymotion can make it difficult for the surgeon to hold the saw steady.Further, because this longer type of saw blade oscillates alongessentially its entire length during the cutting procedure, the sawblade can cause extensive damage to the soft tissue at the incision.

Moreover, a longer blade is more flexible than its shorter counterpart.The added flexibility of the blade can result in the blade making lessprecise cuts in the bone the blade is used to shape. Unfortunately, itis not possible to reduce this flexibility by simply increasing theoverall thickness of the blade. Taking this action increases the mass ofthe blade and, by extension, the mass moment of inertia of the blade.For the reasons set forth above, increasing the mass moment of inertiaof the blade would, in turn, increase the extent to which the associatedsaw, when actuated, vibrates.

Also, both the sagittal saws that are provided with oscillating bladesand the proposed saw with a static guide bar are used with cuttingguides that are relatively large in size. The relatively large size ofthe presently available cutting guides makes it difficult, if notimpossible, to perform a minimally invasive surgical procedure.

U.S. Pat. No. 2,854,981 discloses a surgical saw having a saw bladepivotably supported at the end of a beam which extends forwardly from ahandpiece. The beam includes a pair of tubes which are secured onopposite sides of a support rod, which tubes house therein reciprocatingthrust rods. The thrust rods push against a plate adjacent the blade andcause the blade to undergo pivotal oscillating movement.

This saw, due to the pivotal movement of the blade at the distal end ofthe saw, would not appear to create excessive vibratory motion and/orsoft tissue damage. However, the extension of the saw relative to thecutting slot or kerf created by the blade in the hard tissue or bone islimited. That is, the depth at which the saw can cut is limited to thelength of the blade itself, since the beam which supports the blade ismuch larger than the blade.

Further, the arrangement illustrated in the above patent actuates theblade through compression of the respective thrust rods which then pushagainst the blade to move same. This type of arrangement necessarilyrequires that the rods be dimensionally large and constructed of a heavymaterial capable of repeatedly withstanding these types of forces, whichthen results in a heavy and cumbersome saw.

SUMMARY OF THE INVENTION

This invention is generally related to a new and useful sagittal saw forperforming a surgical procedure and a complementary cutting guide forusing the saw. The saw of this invention has a static, planar guide barthat extends forward from the saw handpiece. A saw blade is pivotallyattached to the distal end section of the guide bar. Drive rods or driveelements are attached to the opposed sides of the blade and are housedwithin the guide bar. The drive rods are attached to a drive assemblyintegral with the saw handpiece.

The saw of this invention is used by actuating a motor internal to thehandpiece. The drive assembly transfers the power developed by the motorto the drive rods so that the rods simultaneously engage inback-and-forth reciprocating motion in opposite directions. The driverods, in turn, transfer the reciprocating motion to the saw blade sothat the blade teeth move in a back-and-forth or side-to-sideoscillating motion.

The pivotal attachment of the saw blade at the distal end of the guidebar results in less vibratory motion of the saw. Further, the staticguide bar which supports the blade avoids excessive wearing of thecutting guide, and particularly slotted cutting guides. Of particularadvantage is the configuration of the guide bar according to theinvention. More specifically, the guide bar is constructed so as to havea relatively small thickness dimension, which in the preferredembodiment is no larger than the thickness dimension of the blade. Thisallows increased extension or advancement of the blade into the bone,since the guide bar is dimensioned so that same will fit into thecutting slot or kerf created by the blade in the bone. Further, thedrive rods are under tension in that same exert a pulling force on theblade to oscillate same. This means that thinner drive rods can beutilized, which results in a lightweight and easy to use saw.

The cutting guide of this invention is defined by a block or body. Pinsor other fastening members hold the guide block in a fixed positionrelative to the bone or other hard tissue to be cut. The cutting guideis formed with one or more outer surfaces that are guide surfaces. Thecutting guide is positioned so that the guide surface is in the plane orimmediately adjacent the plane in which the cut through the bone is tobe made. A capture pin extends upwardly from the guide surface. Theguide bar of the saw of this invention is further formed to have anelongated slot. The cutting guide capture pin is seated in the slot tohold the saw guide bar to the cutting guide, and yet allow the saw toboth move forward and pivot relative to the cutting guide. The capturepin can be slidably mounted or seated within an elongate slot or trackdefined in the block which opens through the guide surface, whichcapture pin is moved by the guide bar of the saw during a cuttingprocedure to allow lateral movement of the saw across the guide surface.Alternatively, the capture pin can be mounted to the block in aremovable manner to allow same to be mounted in multiple locations alongthe block.

The capture pin reduces the overall size of the cutting guide, whichmakes it possible to use a cutting guide that is relatively small insize. Further, the cutting guide according to the invention allowsgreater cutting site visibility of open-face cutting guides as discussedabove. However, the capture pin according to the invention avoids thedisadvantage of conventional open-face cutting guides wherein thesurgeon must make a conscious effort to maintain the saw blade flatagainst the guide surface of the cutting guide.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed out with particularity in the claims. The aboveand further features and advantages are better understood from theDetailed Description below and the accompanying drawings, in which:

FIG. 1 is a perspective view of the saw and saw blade assembly of thisinvention;

FIG. 2 is an exploded view of the head of the handpiece of thisinvention;

FIG. 3 is a longitudinal cross-sectional view of the head of thehandpiece;

FIG. 4 is a lateral cross-sectional view of the head of the handpiece;

FIG. 5 is a perspective view of the drive base;

FIG. 6 is a plan view of the drive link;

FIG. 7 is a plan view of the saw blade assembly of this invention;

FIG. 7A is a cross-sectional view of the distal end of the saw bladeassembly of FIG. 7 along the longitudinal center axis of the saw bladeassembly;

FIG. 8 is an exploded view of the saw blade assembly;

FIG. 9 is a plan view of the saw blade;

FIG. 10 is a perspective view of how the saw and cutting guide of thisinvention are collectively used to make a defined cut in a section ofbody tissue, the body tissue being a diagrammatic representation of aportion of bone;

FIG. 11 is a perspective view of the cutting guide of this invention;

FIG. 11A is an enlarged cross-sectional view of the cutting guide shownin FIG. 11;

FIG. 11B is a top perspective view of an alternative cutting guide;

FIG. 11C is a side view of the cutting guide of FIG. 11B;

FIG. 12 is a plan view of an alternative saw blade assembly of thisinvention;

FIG. 13 is a partially disassembled plan view of the saw blade assemblyof FIG. 12, with the outer bar removed;

FIG. 14 is a plan view of the saw blade of FIG. 13;

FIG. 15 is a perspective view of the distal end of an alternative sawassembly of this invention;

FIG. 16 is a plan view of a partially disassembled saw blade of FIG. 15;

FIG. 17 is a cross sectional view of an alternative saw blade of thisinvention;

FIG. 18 is a side and cross-sectional view of an alternative means ofattaching the saw blade to the cutting guide of this invention;

FIG. 19 depicts the features of an alternative saw blade of thisinvention and how the saw blade is pivotally mounted to thecomplementary guide bar assembly;

FIG. 20 depicts the features of an alternative saw blade of thisinvention and how the saw blade is pivotally mounted to thecomplementary guide bar assembly; and

FIG. 21 depicts the features of another alternative saw blade assemblyof this invention.

Certain terminology will be used in the following description forconvenience in reference only, and will not be limiting. For example,the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” willrefer to directions in the drawings to which reference is made. Thewords “inwardly” and “outwardly” will refer to directions toward andaway from, respectively, the geometric center of the arrangement. Theword “distally” shall mean directed towards the patient, and the word“proximally” shall mean directed away from the patient. Said terminologywill include the words specifically mentioned, derivatives thereof, andwords of similar import.

DETAILED DESCRIPTION

FIG. 1 illustrates a surgical saw 20 and complementary blade assembly 22of this invention. Saw 20 includes a handpiece 24 that functions as thebody of the saw. The handpiece 24 is shaped to have a handgrip 26 and anupper shell 28 that extends over the handgrip 26. Internal to the uppershell 28 is a motor 30 (shown in phantom). A battery (not shown) isremovably attached to the base of the handgrip 26. A manuallyretractable trigger 32 extends forward from the distally directedforward surface of the handgrip 26. Located in the upper shell 28immediately above the trigger 32 and below the motor 30 is a controlmodule 34 (shown in phantom). Electronics integral with the controlmodule 34 monitor the extent to which the trigger is depressed and,based on the trigger state, regulate the actuation of the motor 30.

Located forward from the distally facing front face of the handpieceupper shell 28 is a head 38. Head 38 is the component of the saw 20 towhich the blade assembly 22 is attached. The head 38 is attached to thehandpiece 24 by a cylindrical neck 40, head 38 and neck 40 being formedas an integral unit. The outer surface of neck 40 is provided withthreading (not illustrated). Neck 40 is screw-secured in a forwardopening bore in the handpiece upper shell 28 (bore not illustrated).

As seen in FIGS. 2-4, a lock ring 41 is threaded over neck 40 andlocated forward of the upper shell 28. When the handpiece 24 of thisinvention is assembled, the head 38 and neck 40 are first rotated so asto be in the proper orientation relative to the handpiece upper shell28. Lock ring 41 is then rotated around the neck 40 so as to pressagainst the front face of the upper shell 28 so as to hold the head 38and neck 40 in position.

Head 38 is located at the distal end of the neck 40 and has across-sectional width greater than the diameter of the neck. The distalfacing front face of the head is curved. A bore 42 extendslongitudinally through the neck 40. The bore 42 terminates in a bore 44that extends longitudinally through the head 38. Since the longitudinalaxes of head 38 and neck 40 are perpendicularly offset from each other,it should be understood that the axes of bores 42 and 44 are likewiseperpendicularly offset.

The top of the head 38 is formed so as to define two grooves 46 and 47,each of which has a rectangularly shaped cross-sectional profile. Groove46 extends longitudinally along the head 38, from the distal facingfront face towards neck 40. Groove 47 extends perpendicular to andcrosses groove 46. Groove 47 is deeper than groove 46 such that groove47 bisects groove 46. Bore 44 opens into the top surface of the head 38that defines groove 47.

Internal to head 38 and neck 40 is a drive assembly that actuates theactual saw blade of saw blade assembly 22 that is now described byreference to FIGS. 2 and 3. The drive assembly includes a drive shaft 48that extends from the handpiece upper shell 28 into the neck 40. In someversions of the invention, drive shaft 48 may be the actual output driveshaft of motor 30. In some versions of the invention, drive shaft 48 maybe an output drive shaft of a speed reduction gear assembly or an idlershaft to which the actual motor drive shaft is connected.

The rotation of the drive shaft 48 oscillates, via a drive link 72, agenerally cylindrical, multi-section head drive shaft or drive base 50that is rotatably mounted in head bore 44. The head drive shaft 50, nowdescribed with reference to FIG. 5, is shaped to have a cylindrical stem52. Stem 52 has a first lower section 54 with a first outer diameter anda second upper section 56 with a second outer diameter that is slightlylarger than the first diameter. Above the stem second section 56, headdrive shaft 50 has a main section 58 with an outer diameter greater thanthat of either of the stem sections 54 and 56. Generally, the mainsection 58 is cylindrical. However, the main section 58 is formed sothat the lower section thereof has two diametrically opposed flats 60.Above the main section 58, head drive shaft 50 is formed to have a head62. The head 62 is generally circular in shape and has an outer diametergreater than that of the underlying main section 58. Head 62 is furtherformed to have a slot 64 that extends along the length of the head. Thelongitudinal axis of slot 64 is perpendicular to the planes in whichflats 60 lie.

When the handpiece 26 is assembled, most of the head drive shaft 50 isdisposed in head bore 44. The upper portion of the head 62 extends intothe bottom portion of the head groove 47.

Bearing assemblies 66 and 68 rotatably hold head drive shaft 50 in head38. Bearing assembly 66 extends between the stem lower section 54 andthe adjacent inner wall of head 38 that defines bore 44. The inner raceof bearing assembly 66 abuts the step between the lower and uppersections 54 and 56, respectively, of the stem 52. A retaining ring (notillustrated) snap fitted into a groove 67 formed in the end of the stemlower section 54 holds the bearing assembly 66 to the stem 52.

Bearing assembly 68 is located around the main section 58 immediatelybelow the head 62. Bearing assembly 68 thus extends between the mainsection 58 and the inner wall of the head that defines bore 44. In thedepicted version of the invention the head is shaped so that the bore 44has a large diameter counterbore (not identified). The outer race ofbearing assembly 68 seats against the stepped surface between thecounterbore and main sections of bore 44.

Drive link 72, as best seen in FIG. 6, has a circular distal end 74formed with a closed opening 73. Opening 73 is defined by two opposedflat walls 75 and two opposed curved walls 76. More particularly, thedrive link 72 is shaped so that, when the drive link is fitted to thehead drive shaft 50, the flat walls 75 and curved walls 76 that definethe opening 73 closely abut, respectively, the flats 60 and adjacentcurved surfaces of the main section 58 of head drive shaft 50.

A collar 77 is press-fit to the stem upper section 56. Collar 77prevents downward slippage of the drive link 72 from the main section58.

Extending proximally from the distal end that defines opening 73, drivelink 72 is shaped so as to have a proximal end that has two parallelopposed tines 78. Tines 78 are generally directed towards drive shaft48.

Drive shaft 48 is formed to have a cylindrically-shaped cam 79 thatextends forward from the front end of the drive shaft. Cam 79, it willbe observed, is parallel to and axially offset from the longitudinalaxis of drive shaft 48. The drive link 72 is positioned relative to thedrive shaft so that cam 79 is disposed between the drive link tines 78.

A spherical bearing 80 is fitted over cam 79. The drive shaft cam 79extends into an opening 82 in the center of the spherical bearing 80. Asnap ring 81 holds bearing 80 to the cam 79. Bearing 80 is positionedand dimensioned to be closely slip fitted between the drive link tines78. Thus, bearing 80 transfers the rotational movement of cam 79 aroundthe center axis of the drive shaft 48 to the drive link 72 as anoscillatory movement, and the drive link 72 transfers this oscillatorymovement to head drive shaft 50.

An oscillating bar 86 is secured in the slot 64 formed in the drive basehead 62. More specifically, a threaded fastener (not illustrated) thatextends through an opening 87 formed in the oscillating bar 86 and abore 88 in the head drive shaft 50 that opens into slot 64, holds thebar 86 to the head drive shaft 50. Oscillating bar 86, it will beunderstood is positioned in the base of the head groove 47.Collectively, the assembly that oscillates bar 86 and the bar 86 areconstructed so that, when the bar oscillates, the component does notcontact the opposed interior walls of head 38 that define head groove47.

Two pins 85 are press-fit into separate openings 90 formed in the top ofoscillating bar 86. Openings 90 are centered on the longitudinal axis ofthe oscillating bar 86 and symmetrically located around opening 87. Eachpin 85 has a relatively wide center waist section 84. The presence ofthe waist sections 84 limit the extent to which the pins 85 arepress-fit into the oscillating bar 86.

A cover 91 is secured over the top of the saw head 38 so as to cover theproximal end of the saw blade assembly 22, i.e. the end secured to thehead 38. Cover 91 is shaped so as to have legs 92 that extend downwardlyfrom opposed sides of the cover (one leg shown). The legs 92 seat inopposite ends of head groove 47.

Cover 91 is further formed to have a downwardly extending center rib 94that extends the length of the cover. Rib 94 is spaced inwardly fromlegs 92. When the saw 20 and complementary blade assembly 22 of thisinvention are assembled together, the proximal end of the blade assembly22 is seated in head groove 46. Rib 94 seats in head groove 46 above theproximal end of the blade assembly 22. The rib 94 is formed with twoparallel opposed flanges 98 (one flange shown). Flanges 98, which arelocated on opposed sides of the rib 94, extend the length of the rib.When the saw 20 and blade assembly 22 are assembled together, eachflange 98 is located between a side edge surface of the blade assembly22 and the adjacent inner wall of the head 38 that defines groove 46.

Threaded fasteners 93 removably secure the cover 91 to the head 38. Eachfastener 93 extends through an opening 102 formed with a counterbore 103(FIG. 3) that extends through the cover 91 and rib 94 into acomplementary threaded bore 104 formed in the head 38. Bores 104, itwill be observed extend downwardly from the base of head groove 46.

As seen by reference to FIGS. 1, 7, 7A and 8, the saw blade assembly 22includes a guide bar assembly 110 that extends distally forward fromhandpiece head 38. A saw blade 112 that is pivotally connected to theguide bar assembly 110 extends forward from the distal end of the guidebar assembly. Thin, plate-like drive rods or drive elements 114 extendbetween the oscillating bar 86 located in the head 38 of handpiece 24and the saw blade 112. The drive rods 114 transfer the oscillatingmotion of bar 86 to the saw blade 112 so that when the saw 20 isactuated, the saw blade 112 moves in a back-and-forth motion.

The guide bar assembly 110 consists of three planar, plate-shaped bars,i.e. a bottom bar 116, an inner bar 118 and an outer bar 120 that arestacked together. Bottom bar 116 and outer bar 120 are generallyidentical in overall length and width. The bottom bar and outer bar 116and 120, respectively, are each formed so that immediately forward ofthe proximal end, there are two inwardly directed cutouts 122. The mostdistal front ends of both the bottom bar 116 and outer bar 120 arecurved (curved distal ends not identified). The bottom bar 116 isfurther formed to define opposed rectangular notches 124 that arelocated proximally of the front end and extend inwardly from the opposedsides of the bar.

Inner bar 118 is shorter in overall length and narrower in overall widththan the bottom bar and outer bar 116 and 120, respectively. Inner bar118 is formed to have a proximal end stem 128 with a proximal end edgethat is aligned with the proximal end edges of the surrounding bottombar 116 and outer bar 120. A short distance forward from the proximalend edge, the inner bar stem 128 curves inwardly so as to have acurvature that is aligned with the adjacent inwardly curved side edgesof the bottom bar 116 and outer bar 120. Forward of where the inner bar118 curves inwardly, the bar 118 has a constant width.

Inner bar 118 has an overall length that is typically from 70 to 90% ofthe overall length of the bottom and outer bars 116 and 120,respectively. In more preferred versions of the invention, the overalllength of the inner bar 118 is between 75 and 85% of the overall lengthof the bottom and outer bars 116 and 120, respectively. Forward of stem128, inner bar 118 has a width that is typically between 30 and 95% ofthe width of the bottom and inner bars 116 and 120, respectively. Inmore preferred versions of the invention, the width of the main portionof the inner bar 118 is between 50 and 90% of the width of thesurrounding sections of the bottom and outer bars 116 and 120,respectively.

The guide bar assembly 110 is assembled by first welding a pair ofsupport bars 130 in notches 124 of the bottom bar 116. The support bars130 are generally rectangular in shape. One support bar 130 is welded ineach notch so as to extend upwardly from the bottom bar 116.

The inner bar 118 and outer bar 120 are then stacked over the bottombar. The support bars 130 are welded to the abutting inwardly directedface of the outer bar 120. Once the guide bar assembly 110 is partiallyassembled (i.e. the inner bar 118 is still loose at this point), thesandwiched metal forming the bottom, inner and outer bars 116, 118 and120, respectively, is selectively removed in a single operation to forma generally rectangular guide slot 132 and two oval shaped openings 134and 136. Slot 132 and openings 134 and 136 are longitudinally alignedalong the center longitudinal axis of the bars 116, 118 and 120. Slot132 is located in the portion of the guide bar assembly that extendsforward from saw head 38. The guide bar assembly is further formed so asto define an opening 133 that is contiguous with and communicates withthe distal end of slot 132. Opening 133 is wider than slot 132. Openings134 and 136 are formed in the portions of the guide bar assembly 110that seat in the base of head groove 46. Opening 136 is the moreproximally located of the two openings. Portions of the edge surfaces ofthe bottom, inner and outer bars 116, 118 and 120 that define slot 132and openings 133, 134 and 136 are then welded together so as to securethe bars to each other.

When the blade assembly 22 is attached to saw 20, guide bar openings 134and 136 are each in registration with one of the cover openings 102 andcomplementary head openings 104. Thus, openings 134 and 136 eachaccommodate a separate one of the fasteners 93 that secure the cover 91to the head 38. Fasteners 93 likewise hold the saw blade assembly 22 tothe saw 20. Openings 134 and 136 are oval to accommodate formanufacturing variations between the components of this invention. Thepurpose of the guide slot 132 and companion opening 133 is explainedhereinafter.

It will be appreciated that blade assembly 22 may alternatively besecured to saw 20 without the use of fasteners 93. For example, bladeassembly 22 can be fastened to saw 20 by a detent or other capturearrangement which would allow the proximal end of blade assembly 22 tobe quickly fastened to saw 20.

Guide bar assembly 110 also has a pivot pin 140 formed of hardenedmetal, such as tungsten carbide. Pivot pin 140 is located immediatelyforward of the distal end of the inner bar 118 and extends between thebottom and outer bars 116 and 120, respectively. More particularly, thebottom bar 116 and outer bar 120 are formed with holes 142 and 144,respectively. The opposed ends of the pivot pin 140 are welded orotherwise secured in holes 142 and 144.

From the foregoing description, it should be understood that the innerbar 118 and support bars 130 hold bottom bar 116 and outer bar 120 apartor in spaced relation from each other. Inner bar 118 and the supportbars 130 also contribute to the overall rigidity of the guide barassembly 110.

The saw blade 112 is now initially described in detail by reference toFIG. 9. The saw blade 112 is a single monolithic piece of flat-shapedmetal, such as 420 stainless steel. The saw blade 112 is shaped to havea generally rectangular base 148 that forms the proximal end of theblade 112. Base 148 is shaped to have three notches 150, 152 and 154that extend forward from the proximal end of the base 112. Notch 152,the middle one of the three notches, is U-shaped and is located alongthe longitudinal center axis of the saw blade 112.

Notches 150 and 154 are located on opposed sides of notch 152 and areequidistantly spaced from the longitudinal center axis of the saw blade112. Notches 150 and 154 are identically shaped. Specifically, the sawblade 112 is shaped so that each notch 150 and 154 has a taperedproximal section 156. Specifically, the notch proximal sections aretapered such that the sections have the greatest width adjacent theproximal edge of the saw blade 112. Integral with and located forward ofthe proximal section 156, each notch 150 and 152 has a distal section158 with a circular cross-sectional profile. The diameter of the notchdistal sections 158 is approximately equal to that of the widest widthof the proximal sections 156.

Extending forwardly from the base 148, saw blade 112 has a main section162. In the illustrated embodiment, the main section is formed to havetwo opposed sides 164 that have a concave curvature. Owing to thecurvature of sides 164, the narrowest width portion of the saw blademain section 162 is the middle portion of the main section.

Forward of the main section, saw blade 112 in the illustrated embodimenthas an arcuately shaped head 166. It will be appreciated that blade 112need not be outwardly curved as shown, and instead may have otherconfigurations. Head 166 is formed with teeth 168. The head 166 is theactual cutting portion of the saw blade 112. For the reasons discussedbelow, the blade 112 is formed so that head 166 has a thickness greaterthan that of the base 148 and main section 162.

It is anticipated that saw blade 112 will typically have a side-to-sidewidth of about 1.5 inches or less and often about 0.9 inches or less.The overall length of the saw blade 112 from the proximal end of thebase 148 to the most distal tooth 168 will be about 3.0 inches or lessand often about 1.5 inches or less.

Collectively, the saw blade assembly 22 is constructed so that the bladehead 166 has a depth, i.e. a thickness, greater than that of theadjacent guide bar assembly 110 as shown in FIG. 7A. The saw blade 112is shaped so that the opposed top and bottom surfaces of the blade head166 extend, respectively, above and below the adjacent top and bottomsurfaces of the guide bar assembly 110. As a result of this design, whensaw 20 is actuated and the blade head 166 pressed into the bone, theresultant kerf is slightly larger than the thickness of the guide barassembly 110. This facilitates the movement of the guide bar assembly110 through the kerf as the bone is cut. In practice, it is anticipatedthe saw blade assembly 22 will be designed so the blade head 166 has athickness that is approximately 0.010 inches greater than that of theguide bar assembly 110 from which the head extends. The saw blade 112 isshaped so that the extra thickness of the head 166 is symmetricallyarranged relative to the top and bottom surfaces of the guide barassembly 110. Thus, the blade head 166 typically extends approximately0.005 inches beyond each of the top and bottom surfaces of the guide barassembly.

In saws of this invention with saw blade assemblies 22 designed for usein orthopedic surgery, the guide bar assembly will often have athickness of approximately 0.090 inches. The complementary saw bladehead 166 will therefore have a thickness of approximately 0.100 inches.It is anticipated that the thinnest saw blade assemblies 22 designed fororthopedic surgery will have guide bar assemblies with a thickness of0.040 inches and blade heads with thicknesses of 0.050 inches. Thesethin saw blade assemblies would be designed for use with conventionalcutting guides that are formed with narrow guide slots.

The saw blade 112 is disposed between the distal end sections of thebottom and outer bars 116 and 120, respectively. The saw blade 112 ispositioned between bars 116 and 120 so that the pivot pin 140 seats innotch 152. Saw blade 112 thus pivots around pin 140.

The drive rods 114 connect the saw blade 112 to the opposed ends of theoscillating bar 86. The drive rods 114 are formed of a metal such as17-4 stainless steel. This material has a slight degree of elasticityfor purposes that will be clear from the following description. As seenby reference to FIG. 8, the proximal end of each drive rod 114 is formedto have a ring 170. The distal end of each drive rod 114 is formed tohave a solid, circularly shaped head 172.

When saw 20 and blade assembly 22 of this invention are assembledtogether, each drive rod 114 is located between the bottom and outerbars 116 and 120, respectively and adjacent one side of the inner bar118. The proximal end ring 170 of each drive rod is fitted over aseparate one of the pins 85 integral with the oscillating bar 86. Thedistal end head 172 is seated in the distal section 158 of the adjacentsaw blade notch 150 or 154.

In practice, in the described version of the invention, a saw blade 112is removed and replaced by first removing cover 91 from head 38. The sawblade assembly 22 is then removed from the head 38 so that the drive rodrings 170 are lifted off the pins 85. Once the guide bar assembly 110 isfree of the head, the saw blade 112 is pulled forward so as to exposethe drive rod heads 172. Once the saw blade 112 is so positioned, it isa simple matter to remove the blade from the drive rods 114, fit a newblade to the drive rods and push the blade and drive rods proximallyback towards the saw head 38 to a position where notch 152 engages thepin 140. The reassembled saw blade assembly is then reattached to thesaw head 38.

FIG. 10 illustrates how a cutting guide 180 of this invention is used tohold the saw 20 and saw blade assembly 22 steady so as to facilitate themaking of a desired cut in the bone to which the saw blade 112 isapplied. FIG. 11 shows the cutting guide in an isolated view. Cuttingguide 180, sometimes referred to as a jig, includes a block or body 182which can be affixed to most bone joint resection surfaces. In thedepicted version of the invention, block 182 is generally L-shapedthough this need not always be the case. In practice, cutting guide 180is temporarily fitted to the proximal portion or head 184 of a tibia 186(tibia represented diagrammatically). The cutting guide 180 ispositioned so that the long side of the block extends perpendicularlyacross the proximal portion 184. In FIG. 10, cutting guide 180 is shownspaced rearwardly from head 184 for illustrative purposes. Pins 183 (oneshown) temporarily secure block 182 to the tibia 186. The pins 183extend into the tibia 186 through bores 187 formed in the block 182.

Block 182 in the illustrated embodiment defines therein a groove 188,although this need not always be the case. Groove 188 (FIG. 11) extendsvertically through the long-width end section of the block 182. Thus,groove 188 is generally parallel to tibia 186 and extends inwardly fromthe surface of the block 182 positioned adjacent the tibia 184. Groove188 is shaped to receive an alignment rod used to facilitate thepositioning of cutting guide 180. (The alignment rod is not part of thisinvention.) A thumb screw 190, the head of which is shown in FIG. 11, ismounted to the proximal portion of the block 182 located below the longupper section thereof. The thumb screw 190 projects into groove 188 tofacilitate the temporary securing of the cutting guide 180 to thealignment rod.

The topmost outer surface of block 182, the surface depicted asextending perpendicularly relative to the tibia portion 184, is referredto as the guide surface 194. The guide surface 194 is in a plane thatintersects the tibia, in the illustrated example, the tibia portion 184.

The block 182 defines therein an elongated slot, channel or track 195which opens upwardly through guide surface 194 and extends across asubstantial portion of the long upper portion of block 182. In theillustrated embodiment, the track 195 at one end opens sidewardlythrough a terminal side surface 195A of block 182 and terminates at anopposite closed end adjacent groove 188. With reference to FIG. 11A,track 195 is defined by an upper portion 195B which opens upwardlythrough guide surface 194 and a lower portion 195C which opens into orcommunicates with upper portion 195B. Lower portion 195C has a greaterwidth than upper portion 195B to provide track 195 with an invertedT-shaped or dovetail configuration.

As shown in FIGS. 10-11A, a capture pin or capture element 196 ismovably and slidably mounted within track 195 of block 182. Capture pin196 has an upper enlarged part or head 197 which is located above guidesurface 194, a stem or middle section 198 which is connected to andprojects downwardly from head 197, and a lower part or base 199 which isconnected to and projects downwardly from stem 198. The width dimensionsof stem 198 and base 199 are slightly less than the respective widthdimensions of upper and lower portions 195B and 195C, respectively, toallow sliding movement of capture pin 196 within track 195. Further, thestem 198 of pin 196 is sized so that same can travel within guide slot132 of guide bar assembly 110, and head 197 is sized to have a greaterwidth than guide slot 132. When the capture pin 196 is positioned withintrack 195, the head 197 is spaced upwardly a short distance from guidesurface 194 as shown in FIG. 11A to allow positioning of guide barassembly 110 between head 197 and guide surface 194 as shown in dottedlines and as discussed further below. The space defined between thelower surface of head 197 and guide surface 194 is large enough to allowmovement of guide bar assembly 110 relative to cutting guide 180.

The saw 20 including saw blade assembly 22 and cutting guide 180 areused by first affixing the cutting guide 180 to the bone to be cut withpins 183. More particularly, the cutting guide 180 is secured to thebone so that the guide surface 194 is immediately below the plane of thebone along which the cut is to be made. The saw 20 is then fitted to thecutting guide 180. This is accomplished by passing the capture pin head197 through the wide diameter opening 133 of the guide bar assembly 110.The saw is then moved forward so that stem 198 seats in the guide barassembly slot 132 so as to hold the guide bar assembly, as well as theattached saw 20, to the cutting guide 180. The surgeon then makes thedesired cut by depressing the trigger 32 so as to actuate the motor 30.The actuation of the motor 30 results in the oscillation of bar 86. Themovement of bar 86 is transferred by drive rods 114 to the saw blade 112so as to cause a back-and-forth movement of the blade 112 across thedistal end of the guide bar assembly 110 and about pivot pin 140. Thesurgeon then presses the saw into the bone, tibia portion 184. The cutis made along the desired line by moving the saw so that the guide barassembly 110 pivots around stem 198 of capture pin 196. The saw can bepushed forward so that blade 112 cuts completely through the bone.During the procedure, the guide bar assembly 110 is constrained betweenthe guide surface 194 and the head 197 to ensure that as the blade 112is pressed forward into or towards the bone, the cut in the bone is madein the desired cut plane as determined by guide surface 194. Further,during the cutting process, the capture pin 196 is moved by the guidebar assembly 110 within and along track 195 to allow lateral movement ofthe saw 20.

After the desired cut is made, the saw is retracted so that guide baropening 133 is again in registration with the capture pin head 197. Thesaw is then lifted free of the cutting guide 180 and the cutting guide180 released from the bone.

The saw 20 and saw blade assembly 22 are thus constructed so that theonly exposed component that moves side-to-side is the saw blade head166, the most distal component of the saw. The guide bar assembly 110remains static with respect to the rest of the saw 20. Thus, when thesaw of this invention is inserted in a conventional cutting guide formedwith a guide slot, once the saw blade starts cutting through bone, theonly saw component that abuts the surfaces forming the guide slot arethe surfaces of the guide bar assembly 110. Since the guide bar assemblyis relatively static, this abutment does not excessively wear thematerial defining the slot in the cutting guide. Consequently, thisinvention avoids the problems associated with this wear.

Still another feature of the saw and saw blade assembly of thisinvention, is that the oscillating portion of the saw, blade 112, isrelatively short. Consequently, the mass moment of inertia of the blade,i.e. the inherent ability of the blade to resist changes in rotationalspeed, is relatively small in comparison to longer conventional blades.Since the mass moment of inertia of the saw blade is relatively small,large amounts of force do not have to be applied to the blade in orderto cause it to oscillate in the desired back-and-forth pattern. Giventhat only small amounts of force are applied to the blade, the resultantvibrations induced by the oscillatory movement of the blade are likewisereduced in comparison to those produced when a conventional saw blade isoscillated.

Since the only portion of the saw blade assembly 22 that moves is thesaw blade 112, the mass moment of inertia of the saw blade assembly 22of this invention is independent of the length of the guide bar assembly110. This means a saw blade assembly 22 that includes a guide barassembly 110 with a length of about six inches or more would haveassociated with it the same mass moment of inertia that is present witha saw blade assembly that has a guide bar assembly of shorter length.(This assumes both saw blade assemblies 22 are provided with the samesize saw blade 112.) Thus, using saw 20 with a relatively long saw bladeassembly 22 does not result in the saw vibrating appreciably more thanone when a shorter blade assembly is used. These long length saw bladeassemblies are well suited to make cuts in bone exposed using aminimally invasive surgical technique, and are otherwise difficult toaccess. Thus, the saw of this invention can be used to perform minimallyinvasive surgery with a relatively long blade assembly without vibratingsignificantly more than when the saw is used to perform a procedure witha short-length blade assembly.

Still another benefit of the saw and saw blade assembly of thisinvention is that since the saw blade 112, and not the guide barassembly 110, is the oscillating component, the guide bar assembly 110can be made relatively thick without increasing the mass moment ofinertia of the saw blade assembly 22, while still maintaining athickness which is small enough to be inserted into the kerf made in thebone by the blade head 166. It may be useful in some embodiments toconstruct the guide bar assembly 110 so that it is relatively thick,i.e. having a depth greater than the dimensions stated above, whenproviding a relatively long length guide bar assembly. The increasedthickness of the guide bar assembly reduces the flexibility of theassembly. This is desirable when providing a long length saw bladeassembly 22 designed to perform a minimally invasive surgical procedure.

The fact that the guide bar assembly 110 stays static further makes itpossible to use the saw 20 of this invention with the complementarycutting guide 180. Cutting guide 180, unlike a conventional cuttingguide, does not require a top wall to define a guide slot or sidemembers to support a top wall-defining upper member. Thus, cutting guide180, since it does not have the structural members of conventionalslot-defining cutting guides, is smaller in size than conventionalcutting guides, and thus provides greater visibility to the surgeon.Further, since there is no contact between the oscillating saw blade 112and the guide surface 194, galling of the guide surface 194 isprevented.

Collectively, it should be further understood that the saw bladeassembly of this invention is designed so that when the saw is actuated,the saw blade moves in an arc of at least about 8° and more preferablyapproximately 10°, (5° on both sides of the longitudinal centerline ofthe guide bar assembly). Constructing the saw and saw blade assembly ofthis invention so that the saw blade moves to this extent results in theblade moving over the same arcuate distance as a conventional sagittalsaw blade, i.e. where a blade is pivotally attached to the head. Thus,since the sweep of the blade of this invention is the same as the bladesweep of a conventional blade assembly, a surgeon will not have tomodify his/her practices significantly to adjust for the use of thisinvention. It is anticipated that when the saw is actuated, blade 112will engage in between about 8,000 and about 16,000 completeback-and-forth oscillations per minute.

FIGS. 11B and 11C illustrate an alternative cutting guide 180′. Cuttingguide 180′ is similar to cutting guide 180, and therefore the samereference numbers are utilized for similar components, plus a “prime”.

Cutting guide 180′ is defined by a generally L-shaped body or block182′. Block 182′ is secured to a bone with pins (not shown) which extendthrough bores 187′ defined in block 182′. Groove 188′ is defined inblock 182′ for receiving an alignment rod. A thumb screw 190′ in thisembodiment is mounted to the short downwardly projecting portion 181 ofthe block 182′ which extends below the long upper section thereof, whichthumb screw 190′ projects into the groove 188′ to temporarily secureguide 180′ to the alignment rod.

In this embodiment, a capture pin or capture element 196′ is mounted toblock 182′ and projects upwardly from guide surface 194′. Capture pin196′ includes an upper part or head 197′ spaced upwardly from guidesurface 194′ by a stem 198′ which extends between surface 194′ and theunderside of head 197′. Stem 198′ has a cross-section which is less thanthat of head 197′, and is sized to allow same to travel within guideslot 132 of guide bar assembly 110. Head 197′ is sized to allow same topass through wide diameter opening 133 of the guide bar assembly 110.The cutting guide 180′ is used in a similar manner as guide 180, andmaintains guide bar assembly 110 between head 197′ and surface 194′during the cutting procedure.

As shown in dotted lines in FIG. 11B, the capture pin 196′ can beremovably mounted to block 182′, and block 182′ can be provided withmultiple mounting locations 185 (shown in dotted lines) to allowselective positioning of capture pin 196′ along guide surface 194′. Anexample of a threaded-type of removable mounting is illustrated in FIG.18 as discussed below.

It will be appreciated that cutting guides 180 and 180′ are onlyexamples of cutting guides which may be used according to the invention,and that other cutting guides may be utilized for securing to otherlocations along the tibia or for attachment to other bones. Further,while cutting guides 180 and 180′ are described herein with reference toguide surfaces 194 and 194′, respectively, it will be understood thatsuch guides may be provided with multiple guide surfaces, if desirableor necessary. In this regard, block 182 can be provided with additionaltracks similar to track 195 which open through the respective guidesurfaces. Likewise, block 182′ can be provided with additional mountinglocations 185 on the respective guide surfaces.

FIGS. 12-14 illustrate an alternative saw blade assembly 210 of thisinvention. Saw blade assembly 210 includes a guide bar assembly 212. Asaw blade 214 is pivotally mounted to the guide bar assembly 212 toextend out of the distal end of the guide bar assembly. Two drive rods216 are integrally formed with the saw blade 214 and extend proximallyrearward from the opposed sides of the saw blade. Each drive rod 216 isconnected to a one of the oscillating bar pins 85.

Guide bar assembly 212 includes a bottom bar 218, an inner bar 220 andan outer bar 222. Bottom bar 218 and outer bar 222 are identicallyshaped and have the general shape of the previously described bottom andouter bars 116 and 120, respectively, of guide bar assembly 110.

Inner bar 220 has a proximal end 224 identical in shape to that of theproximal ends of the surrounding bottom and outer bars 218 and 222,respectively. Forward of the proximal end 224, inner bar 220 is formedto have two symmetric inwardly directed cutouts 226 that define asurface area identical to those defined by the cutouts integral with thebottom and outer bars 218 and 222, respectively. Forward of the cutouts226, inner bar 220 has a main section 228 that extends distally forward.The inner bar 220 is shaped so that main section 228 has a width that isnarrower than the width of the surrounding sections of the bottom andouter bars 218 and 222, respectively. The inner bar 220 is furthershaped so that the main section 228 gives the inner bar an overalllength that is slightly less than the overall length of the bottom andupper bars 218 and 222, respectively. The main section 228 is shaped tohave a distal end front face 229 that has a curved profile.

Guide bar assembly 212 is assembled by stacking the bottom, inner andouter bars 218, 220, and 222, respectively, together. A common slot 230,oval openings 232 and 234, and opening 231 are formed in the bars218-222 in a single operation. Slot 230 extends close to the distal endof the guide bar assembly 212 in which the distal end of the inner bar220 that defines front face 229 is located, and terminates in therectangular opening 231 which is contiguous with slot 230. The abuttingedge surfaces of the bars 218-222 that define slot 230 and openings 232and 234 are welded together to secure the bars together.

Saw blade 214 and drive rods 216, now described by reference to FIG. 14,are formed from a single piece of metal such as 420 stainless steel. Sawblade 214 includes an arcuately shaped base 238. Extending forward frombase 238, saw blade 214 in the illustrated embodiment has an arcuatelyshaped head 240. It will be appreciated, however, that the head 240 mayhave other configurations. Head 240 is the portion of the saw blade 214that extends forward from the guide bar assembly 212 and is the portionof the saw blade on which the teeth are formed. Head 240, likepreviously described saw blade head 166, is larger in thickness than theproximal located base 238 to which the head is attached. Saw blade head240 is of a relatively large thickness for the same reason saw bladehead 166 is similarly shaped.

Drive rods 216 extend proximally rearward from the opposed side edges ofthe blade base 238. The portion of each drive rod 216 that is actuallyattached to the blade base 238 is a narrow width finger 242. Extendingproximally from the finger 242, each drive rod 216 has a main section244 which has a slightly greater width than finger 242. Moreparticularly, it will be observed that the fingers 242 are located sothat their outer surfaces are in line with the outer surfaces of the rodmain sections 244. A ring 246 similar in shape and identical in functionto drive rod ring 170 is integrally attached to the proximal end of eachdrive rod main section 244.

Saw blade 214 will have the same general side-to-side width andthickness as blade 112. The length of the blade, along a radial linefrom a proximal end edge of the base 238 to the distal point of a toothwill usually be less than about 1.0 inches and, more particularly, lessthan about 0.5 inches.

The saw blade assembly 210 of this embodiment of the invention isassembled together by inserting the saw blade 214 between the bottom andouter bars 218 and 222, respectively, of the guide bar assembly 212. Thesaw blade 214 is positioned so that the proximally facing curved end 239of the blade base 238 abuts the similarly curved distal facing face 229of the inner bar 220. Drive rods 216 extend in the space between thebottom and outer bars 218 and 222, respectively, adjacent the opposedsides of the inner bar 220. The proximal ends of the drive rods 216 andthe associated rings 246 extend into the open space of the guide barassembly proximal end cutouts as shown in FIG. 12.

The saw blade assembly 210 of this version of the invention is fitted tosaw 20 and used in the same general manner as saw blade assembly 22. Theproximal end of the guide bar assembly 212 is seated in groove 46 withinsaw head 38. The fasteners used to hold cover 91 to the saw head 38extend through openings 232 and 234 to hold the guide bar assembly 212to the head 38. Drive rod rings 246 are fitted over pins 85 to connectthe saw blade to the oscillating bar 86.

A saw 20 with blade assembly 210 of this invention is used in the samegeneral manner as a saw 20 with blade assembly 22. In this embodiment,the fingers 242 are flexible, such that when drive rods 216 reciprocatein opposite directions, the curved end 239 of blade base 238 moves in areciprocating manner over the distal facing face 229 of the inner bar220, as indicated by arrow 238′ in FIG. 13, which in turn causesside-to-side pivoting movement of the blade head 240 across the distalend of the guide bar assembly 110. Thus, flexible fingers 242 allow thebase 238 and head 240 to pivot relative to the distal end of the guidebar assembly 212.

It will be noted that the slot 230 of guide bar assembly 212 extendsfurther distally along the assembly than slot 132 of guide bar assembly110. This may make it possible to place a capture pin of the cuttingguide designed to be used with guide blade assembly 212 closer to thebone to be cut than is possible with a cutting guide 180 designed to beused with guide bar assembly 110.

FIGS. 15 and 16 illustrate the distal end of an alternative saw bladeassembly 260 of this invention. Assembly 260 includes a housing 262 thatextends forward from the distal end of the handpiece. Housing 262 has aproximal section 264 that is generally cylindrical and that extendsforward from the handpiece. Forward of proximal section 264, housing 262has a middle section 266 that is cylindrical and arranged so as to havea longitudinal axis that is perpendicular to the longitudinal axis ofthe proximal section 264. Forward of middle section 266, housing 262 hasa forward extending planar distal section 268. Distal section 268, itwill be understood, is longitudinally axially aligned with proximalsection 264. Owing to its planar shape, distal section 268 is understoodto be the guide bar of saw blade assembly 260.

Housing proximal section 264 is formed with a longitudinally extendingthrough bore 270 in which a drive shaft 272 is disposed. Also seen inthe drawings are bearing assemblies 274 that rotatably support the driveshaft 272 in bore 270. The drive shaft 272 is connected to a crank 276that is rotatably mounted in a cylindrical space 278 within housingmiddle section 266. Bearing assemblies 280 rotatably hold crank 276 inthe housing middle section 266.

Drive shaft 272 is formed with a head 282 that is in the form of a bevelgear. The shaft head 282 engages a complementary bevel gear 284 formedintegrally with the crank 276 so that rotation of the drive shaft 272results in like movement of the crank 276.

Housing distal section 268 is shaped to define a planar blade space 286that extends proximally rearward from the open front end of the housing262. A saw blade 288 is pivotally mounted in blade space 286. The sawblade 288 consists of a planar, bar-like base 290. A pivot pin 292integral with the housing distal section extends through an opening 290Ain the proximal end of the blade base 290 to pivotally hold the blade288 to the housing 262. In the illustrated embodiment, saw blade 288 isfurther formed to have an arcuately shaped head 294 with teeth 295,which head 294 is attached to the distal end of the blade base 288. Head294 is the only portion of the blade 288 that is located outside ofhousing 262 and is located adjacent the distal front end of the housing.

A pair of push rods 296 connect the saw blade 288 to the crank 276. Thepush rods 296 are located in parallel spaced apart slots 296A formed inthe housing distal section 268. The distal ends of the push rods 296 areconnected to the proximal end of the saw blade base 290 on opposed sidesof the pivot pin 292. The distal end of each push rod 296 is pivotallyattached to the adjacent proximal end of the adjacent blade base 290.The proximal end of each push rod is connected to the crank 276. Theproximal end of each push rod 296 is connected to a pin integral withthe crank 276 that is axially offset from the center axis of the crank.Collectively, the pins to which the push rods 296 are connected arediametrically opposed to each other relative to the center axis of thecrank 276.

While not illustrated, it should be understood that the housing distalsection 268 of this embodiment of the invention may be provided with alongitudinally extending guide slot to facilitate the insertion of thecutting guide capture pin.

Saw and blade assembly 260 of this version of the invention is used byactuating the saw motor so as to cause drive shaft 272 to rotate. Therotation of the drive shaft results in the like rotation of crank 276.The rotation of the crank causes push rods 296 to reciprocateback-and-forth. More particularly, owing to how the push rods areconnected to the crank 276, as one push rod is urged forward, towardsthe distal end of the housing, the other push rod is pulled in theopposite direction. The reciprocating movement of the push rods 296causes a like side-to-side reciprocating or oscillating movement of thesaw blade 288.

It should be understood that the foregoing is directed to specificversions of this invention and that other versions of this invention mayvary from what has been described.

For example, in the above description, in order to remove saw blade 112from the guide bar assembly 110, it is necessary to remove the cover 91from the saw head 38 and wholly remove the saw blade assembly 22 fromthe saw head. Alternatively, it may be possible to simply loosen thefasteners 93 that hold saw cover 91 to the head 38. Since the guide barassembly openings 134 and 136 through which the fasteners 93 extend areoval in shape, once the screws are so loosened, one could then push theguide bar assembly 110 rearwardly. The rearward movement of the guidebar assembly 110 exposes the proximal end of the saw blade 112 so theblade can be removed and new blade connected to the drive rods 114.

In still another alternative version of the invention, the guide barassembly 110 is moveably attached to the saw head 38 such that the guidebar assembly is able to slide towards or away from the saw handpiece 24.A thumb screw or clamp is set to normally hold the guide bar assembly110 in the most forward distal position. When it is desirable to removeand replace the saw blade 112, the thumb screw/clamp is set to releasethe clamping force against the guide bar assembly. Manual force is usedto push the guide bar assembly 110 towards the handpiece 24. Thisdisplacement of the guide bar assembly 110 exposes the proximal base 148of the saw and the distal end heads 172 of the drive rods 114. Theexposure of these components makes it possible to remove the attachedsaw blade 112 from the drive rods 114 and attach a replacement blade.The thumb screw/clamp is then reset to the position in which it locksthe guide bar assembly 110.

In these versions of the invention, a spring may be seated in the headto bear against the guide bar assembly 110. The spring would urge theguide bar assembly to the most distal position. However the thumbscrew/clamp is also provided since when the saw is pressed against thebone, unless there is a locking mechanism, the whole of the saw bladeassembly 22 would be forced rearwardly. Alternatively, a single cammingmechanism may be provided to both normally hold the guide bar assemblyin the most forward position and retract the assembly when it isnecessary to change saw blades 112.

Also, it should likewise be understood that the disclosed type of motivepower used to actuate the saw blade of this invention is understood tobe illustrative, and not limiting. There is no requirement that allversions of this invention include handpieces that are battery powered.The invention can be, if appropriate, constructed using versions of thisinvention wherein the electric power to supply the motor comes from apower supply over a corded link. Also, similarly, the invention is notlimited to handpieces that include electric powered motors. In someversions of the invention, it may be desirable to provide the handpiecewith a pneumatically driven motor. In these versions of the invention,the compressed air used to actuate the motor is supplied to thehandpiece from a hose connected to an air supply.

Moreover, there is no requirement that a power-producing motor beprovided in each handpiece of the saw of this invention. It may bedesirable to provide a version of the saw of this invention wherein themotive unit that generates power is a unit that is separate from andlocated proximal to the handpiece. In these versions of the invention, aflexible drive shaft or a drive cable that extends between the unit withthe motor and the distal located handpiece from which the guide bar andsaw blade extend may be utilized.

Likewise, it should be recognized that the handpiece shape is understoodto be merely exemplary. In an alternative version of the invention, thehandpiece may have an elongated cylindrical shape. This would allow thesurgeon to hold the handpiece much as he/she would hold a large marker.

Alternative means to oscillate the saw blade may be employed. Forexample, there is no requirement that in all versions of the inventiontwo drive rods/push rods be employed. A version of this invention inwhich a single drive rod/push rod that reciprocates back-and-forthoscillates the saw blade may also be possible. The invention could evenbe provided with three or more drive rods that actuate the saw blade.

Similarly, there is no requirement that in all versions of theinvention, the blade consist of a rigid member from which teeth extenddistally outward. In some versions of the invention, the saw blade mayactually be a section of a flexible band of metal. As seen in FIG. 17,in these versions of the invention, a band 302 is formed with a distalend section 306 from which teeth 308 extend outwardly. This distal endsection 306, it is observed, includes both an arcuate center portion 309and two opposed side portions 310. Extending proximally from the opposedside portions 310, band 302 has proximal sections 312. Rings 314 areattached to the proximal ends of the proximal sections 312. In thedepicted version of the invention, the cross-sectional width of theproximal sections 312 is greater than that of the distal end section 306though that may not always be the case.

In this embodiment, the distal end section 306 of the band 302 forms theactual saw blade. This band is wrapped around the guide bar assembly.More particularly, the front end of the guide bar assembly may be formedwith a forward-facing groove in which the center section of the band isseated. The more proximal portions of the guide bar assembly are formedwith channels for accommodating the side sections of the band. Rings 314at the proximally located ends of the band 302 connect the band tooscillating bar 86.

In this version of the invention it will be noted that teeth 308 notonly project outwardly from the front center section 309 of the sawblade, they also project out from the side portions 310. Thus, thisversion of the invention is useful if one wants to cut from the sideedge of the guide bar assembly. As shown in dotted lines in FIG. 17,teeth 308A may also be provided on one or both proximal sections 312 ofband 302 which would project sidewardly through a corresponding openingin the guide bar assembly.

Moreover, it should be appreciated that, in versions of the inventionwith rigid saw blades, there is no requirement that the complementaryconnecting members that extend to the reciprocating drive assembly inthe handpiece be rigid drive rods. In some versions of the invention,flexible drive cables may be employed as the connecting members.

Also, there is no requirement that, in all versions of the invention,the connecting members that extend from the drive assembly extendinternally through the guide bar to the extent the described andillustrated connecting members extend through the guide bar. In someversions of the invention, the connecting members may be seated ingrooves formed in an outer side or edge surface of the guide bar. Theconnecting members may also, along a substantial length of the guidebar, simply lie adjacent the guide bar.

It should similarly be recognized that alternative mechanisms other thanthe described ring-over-pin may be used to connect the saw drive rods tothe oscillating assembly. In some versions of the invention, theoscillating bar may be formed with slots. The proximal ends of the driverods are dimensioned to tightly fit in the slots. Stops are integrallyattached to the drive rods so as to be located on opposed sides of thesection of the rod seated in the oscillating bar slots. Thus, thepresence of the stops ensures that the oscillations of drive rods willcause reciprocal motion of the drive bar. Further, oscillating bar 86which is pivoted or oscillated about the axis defined by head driveshaft 50 may be replaced with a pair of pins or pegs which move linearlyand reciprocate in opposite directions.

It should likewise be understood that there may be variations in how thesaw of this invention is used with the cutting guide. For example, thereis no requirement that in all versions of this invention the cuttingguide be used with a saw blade that oscillates. In some versions of thisinvention, it may be desirable to provide a saw with a blade that is inthe form of an endless band. In these versions of the invention, theband may be driven in a single direction or, alternatively, oscillate.In either version, the band will be mounted to a planar guide barassembly similar to one of the above illustrated and describedassemblies. In these versions of the invention, the guide bar assemblywill have the guide slot previously described to facilitate the seatingof the cutting guide capture pin 196.

As discussed above with respect to cutting guide 180′ of FIGS. 11B and11C, the capture pin may be removably attached to the cutting guide andthe-cutting guide provided with a number of different means for holdingthe capture pin at different points along the guide surface of thecutting guide. An advantage of this arrangement allows the point on theguide surface of the cutting guide at which the guide bar is held to beselectively set.

For example, as seen by FIG. 18, an alternative capture pin 322 may havea generally spool-like shape. The capture pin 322 is assembled so thatthe narrow diameter center section of the pin slidably fits in thelongitudinally extending slot 132 a of a guide bar assembly 110 a. Giventhe permanent or semi-permanent mounting of the capture pin 322 to theguide bar assembly 110 a, there may not be a need to form the guide barassembly with an opening integral with the slot 132 a to facilitate theseating and removal of the guide pin. Here, the guide pin 322 has adownwardly directed threaded stem 324. In these versions of theinvention, the cutting guide block 182 a is formed with a number ofspaced apart threaded bores 326 that extend inwardly from the guidesurface 194 a. The bores 326 are each shaped to releasably hold thecapture pin stem 324.

Alternatively, in these versions of the invention, a spring-biased ballmounted to either the capture pin or the cutting guide may be used toreleasably hold the pin to the cutting guide. A toggle clamp mechanismmay also be employed to hold the capture pin to the cutting guide.

An advantage of the above-described versions of the invention is that itwould allow the surgeon in a single operation to attach both the capturepin 322 and the saw to the cutting guide at the appropriate surfacepoint along the cutting guide.

Likewise, the cutting guide may have alternative constructions from whathas been described and illustrated. At the simplest, a cutting guide maybe formed to have plural guide surfaces each provided with a capture pinfor restraining and guiding the guide bar during the cutting process.Also, it should be recognized that the illustrated version of theinvention, wherein the cutting guide surface essentially abuts the bone,is exemplary, and not limiting. In some versions of the invention, thecutting guide may be shaped so as to have a guide surface that is spacedfrom the tissue or bone in which the cut line defined by the guidesurface is to be formed. This version of the invention may be especiallyuseful in minimally invasive surgical procedures since it would minimizethe amount of hardware it would necessitate placing in close physicalproximity to the bone on which the surgical procedure is to beperformed.

Moreover, while not illustrated, it should be recognized that it may bedesirable to provide the portion of the cutting guide block that definesthe proximal facing edges of the guide surface with posts. These postswould be offset from the capture pin. The posts would be provided if itis desirable to limit the extent to which the guide bar is able to pivotaround the capture pin.

Some versions of the invention provided with the posts may beconstructed so that the posts are spaced essentially the width of theguide bar assembly. The posts would thus essentially stop pivoting ofthe guide bar assembly 110 and the saw 112. In these versions of theinvention, the guide bar assembly may be provided with a small arcuateslot that extends inwardly from the side. A precise arcuate cut is madeby pushing the saw blade assembly forward until the slot goes intoregistration with the post. The guide bar assembly is then pivoted tothe extent the cutting guide post seats in the guide bar side slot.

It should likewise be recognized that alternative means may be providedto hold the cutting guide in a fixed position relative to the bone to becut. For example, a brace assembly may be used to both hold the bonesteady and hold the cutting guide in a fixed position relative to thebone and also in a position that is away from the bone. Thus, in thisparticular version of the invention, since the cutting guide is spacedaway from the bone, it would reduce the need to make incisions aroundthe bone to facilitate cutting guide placement. Thus, this particularversion of the invention would further facilitate cutting the bone usinga minimally invasive surgical procedure.

Moreover, the saw blades may have shapes and features different fromwhat has been shown. For example, saw blades 112 and 214 are depicted ashaving heads with arcuately shaped distally directed faces. This isexemplary and not limiting. As depicted in FIG. 19, it may be desirableto provide a saw blade 330 with a head 332 that has a distal facing face334 that is planar in shape or straight-edged. This version of the sawblade may be provided when it is desirable to provide a saw blade thatcuts more aggressively than an arcuate blade.

Saw blade 330 also has a geometric feature to facilitate the pivoting ofthe blade that is different from that previously described.Specifically, saw blade 330 has a V-shaped pointed tab 334 that extendsfrom the proximally directed end 335 of the blade. Tab 334 seats in aforward opening notch 336 formed in a static component 338 integral withthe guide bar assembly to which the saw blade is mounted. In FIG. 19,the static component 338 represents a pivot pin of the guide barassembly.

Also, there is no requirement that the geometric features that a sawblade is provided with be designed to allow the blade to pivot relativeto the associated drive rods. The proximal end of saw blade 330 isprovided with square shaped openings 340 that are spaced inwardly fromthe blade proximal end 335. A small slot 342 extends from each opening340 to the adjacent proximal end 340.

Saw blade 330 is actuated by drive rods 344. (The distal end of onedrive rod shown.) Each drive rod 344 is provided with a square shapedhead 346. Thus, the rod heads 346 are dimensioned to fit closely withinthe complementary saw blade openings 340. Extending proximally from thehead 346, each drive rod 340 has a flexible elongated neck 348. Thedrive rod necks 348 are the portions of the drive rods that extendthrough and proximally beyond saw blade slots 342. Thus, in versions ofthe invention in which drive rods 344 are employed, the drive rod heads346 do not move relative to the saw blade. Instead, the flexibility ofthe drive rod necks 348 is what allows the pivoting movement of the sawblade relative to the proximal portions of the drive rods 344.

FIG. 20 illustrates still another alternative saw blade 350 of thisinvention. The distal portions of saw blade 350 are similar to those ofthe first-described saw blade 112. Saw blade 350 is, however, providedwith a tail 352 formed of flexible metal. The distal end of tail 352seats in a U-shaped slot 354 that extends forward from the proximal endof the blade 350. The portions of the tail proximal to the saw blade 350seat in a slot 356 formed in a static portion of the guide bar assembly.In FIG. 20, slot 356 is formed in a static pivot pin 358 of the guidebar assembly. Tail 352 is thus the component of the saw blade 350 thatconnects the blade to the complementary guide bar assembly.

It should be clear that the features of saw blades 330 and 350 may beindividually incorporated into the other described saw blades of thisinvention.

Also, the described and illustrated versions of the guide bar assemblyare of uniform thickness along their lengths. This should not beunderstood to be limiting. In alternative versions of the invention, theguide bar assembly may have a thickness that varies along the length.For example, it may be desirable to construct the guide bar assembly sothe proximal portion has a thickness greater than the distal portion.This construction may be appropriate in order to reduce the flexibilityof the guide bar assembly.

Moreover, in the described versions of the invention, the angularpositions of the guide bar assemblies relative to the handpieces fromwhich the assemblies extend are fixed. This need not always be the case.In some versions of the invention, it may be possible to construct theinvention so the angular position of the guide bar assembly, andtherefore of the attached saw blade, relative to the handpiece isselectively set. This may be accomplished by providing a version of theinvention in which the handpiece head and the drive assembly componentsinternal to the head are able to rotate around the axis of the handpiecedrive shaft that actuates the drive assembly. This would make itpossible to set the angular orientation relative to the longitudinalaxis of the handpiece of the plane in which the guide bar is orientedand in which the saw blade oscillates. Thus, one guide barassembly-and-saw blade orientation would be the illustrated orientationwherein the blade is in a plane located about the drive shaft axis. Byresetting the orientation of the head, the saw blade could be placed ina plane that is to the side of the drive shaft axis or even in a planebelow the drive shaft axis.

An advantage of these versions of the invention is that it would allowthe surgeon to set the position of the saw blade so that it is in anoptimal location to facilitate the ergonomic use of the saw of thisinvention.

Moreover, while it is anticipated that, in many versions of theinvention, the saw blade will project forwardly from the distallydirected front face of the guide bar, that may not always be the case.FIG. 21 illustrates an alternative saw blade assembly 360 of thisinvention. Saw blade assembly 360 includes a guide bar assembly 362 ofwhich only a single outer bar 364 is shown.

A saw blade 366 is disposed inside the distal end of the guide barassembly 362. Saw blade 366 has an L-shaped base 368 having proximal end369 with a longitudinal axis that is normally parallel to, if notaligned with, the longitudinal axis of the guide bar assembly 362. Base368 also includes a front end 370 forward of the proximal end that has alongitudinal axis perpendicular to the longitudinal axis of the guidebar assembly. A saw head 372 with teeth 373 extends forward from thefront end 370 of the saw blade base 368.

Collectively, the guide bar assembly 362 and saw blade 366 aredimensioned and arranged relative to each other so that the saw bladehead extends out from a side edge 375 of the guide bar assemblyimmediately proximal to the distally directed front face 372 of theguide bar assembly.

A notch 374 extends forward from the proximal edge of the saw blade baseproximal end 369. The saw blade 366 is mounted to the guide bar assembly362 by positioning the blade so a static pivot pin 376 integral with theguide bar assembly seats in notch 374. Drive rods 378 attached to thesaw blade base 368 on opposed sides of the notch 374 connect the sawblade to the drive assembly integral with the saw. Thus, when the saw ofthis invention is actuated, the drive rods 378 cause the saw blade headto pivot in an arc that is generally parallel to the longitudinal axisof the guide bar assembly.

Saw blade assembly 360 thus provides a version of this invention whereinthe blade 366 can be pressed against bone or hard tissue to make a cutthat is in a direction perpendicular to the longitudinal axis of theguide bar assembly 362. This may be useful where for surgical reasons itis difficult or undesirable to make a cut through bone or hard tissuefrom a head-on direction.

In the above described version of the invention, it should be understoodthat often the pivot pin 376 is positioned on the guide bar assembly 362so that when the saw blade 366 is fitted over the pin, the curvedprofile of saw head 372 is generally centered relative to the pin.

It will be appreciated that the means used to transfer the rotary motionof the motor shaft to the drive rods that oscillate the saw blade may bedifferent from what has been described. Thus, the motor output shaft mayactuate a crank similar to crank 276. Drive rods similar to drive rods114 may be attached to the crank. Upon the actuation of the motor, thereciprocal motion of the drive rods would then cause the oscillation ofthe attached saw blade 112.

Although a particular preferred embodiment of the invention has beendisclosed in detail for illustrative purposes, it will be recognizedthat variations or modifications of the disclosed apparatus, includingthe rearrangement of parts, lie within the scope of the presentinvention.

What is claimed is:
 1. A blade assembly for use with a surgical saw,said blade assembly comprising: a static guide bar comprising a distalend and a proximal end defining a length of said static guide bar; ablade at least partially disposed within said distal end of said staticguide bar; and at least one drive member connected to said blade withinsaid static guide bar, wherein said blade is the only oscillatingcomponent of said blade assembly when said at least one drive member isdriven by the surgical saw.
 2. The blade assembly of claim 1, whereinsaid static guide bar is thicker at said proximal end than said distalend.
 3. The blade assembly of claim 1, wherein the mass of the othercomponents of said blade assembly does not alter the mass moment ofinertia of said blade assembly.
 4. The blade assembly of claim 1,wherein said static guide bar comprises: a first outer bar and a secondouter bar; wherein said first outer bar and said second outer bar definea void in said distal end of said static guide bar; and wherein saidblade is at least partially disposed between said first outer bar andsaid second outer bar within said void.
 5. The blade assembly of claim4, wherein said blade comprises: a base defining a proximal portion ofsaid blade; and a head defining a distal portion of said blade; whereinsaid base is at least partially disposed between said first outer barand said second outer bar in said void.
 6. The blade assembly of claim5, wherein said head of said blade further comprises teeth that arepositioned distally of said distal end of said static guide bar.
 7. Theblade assembly of claim 5, wherein said base of said blade furthercomprises: a pivot positioned on a longitudinal center axis of saidblade; and a notch spaced-apart from said pivot.
 8. The blade assemblyof claim 7, wherein said static guide bar further comprises a pivot pindisposed between said first outer bar and said second outer bar; whereinsaid pivot pin is seated within said pivot of said blade; and whereinsaid at least one drive member is connected to said notch and configuredto oscillate said blade about said pivot pin relative to said staticguide bar.
 9. The blade assembly of claim 7, wherein said at least onedrive member comprises a first drive member and a second drive member;and said blade comprises a first notch and a second notch, each of saidnotches disposed on opposing sides of said pivot; wherein said firstdrive member is connected to said first notch and said second drivemember is connected to said first notch, said first drive member andsaid second drive member configured to simultaneously reciprocate inopposing directions to oscillate said blade about said pivot pinrelative to said static guide bar.
 10. The blade assembly of claim 1,wherein said static guide bar further comprises an inner bar disposedbetween a first outer bar and a second outer bar, said inner bar havinga distal end that is positioned proximally to said distal end of saidfirst outer bar and said second outer bar.
 11. A surgical systemcomprising: a blade assembly having a proximal portion and an opposingdistal portion, said blade assembly comprising: a static guide barcomprising a distal end and a proximal end; a blade at least partiallydisposed within said distal end of said static guide bar; and at leastone drive member connected to said blade within said static guide bar; asurgical saw for actuating said blade assembly, said surgical sawcomprising: a motor comprising an output shaft; and a linkage connectedbetween said motor output shaft and said at least one drive member ofsaid blade assembly to reciprocate said at least one drive member whensaid motor is actuated; wherein said blade is the only component of saidblade assembly that oscillates when said at least one drive member isreciprocated by said surgical saw.
 12. The surgical system of claim 11,wherein said surgical saw further comprises a head having a receivingsurface, said receiving surface shaped to receive said proximal portionof said blade assembly.
 13. The surgical system of claim 12, whereinsaid surgical saw further comprises a clamp assembly attached to saidhead for releasably pressing said proximal portion of said bladeassembly against said receiving surface so as to releasably hold saidstatic guide bar of said blade assembly static when said at least onedrive member is reciprocated.
 14. The surgical system of claim 11,wherein said static guide bar comprises: a first outer bar and a secondouter bar defining a void in said distal end of said static guide bar;and said blade of said blade assembly further comprises: a base defininga proximal portion of said blade; and a head defining a distal portionof said blade; wherein said base is at least partially disposed betweensaid first outer bar and said second outer bar in said void.
 15. Thesurgical system of claim 11, wherein said base of said blade furthercomprises: a pivot positioned on a longitudinal center axis of saidblade; a notch spaced-apart from said pivot; and said static guide barfurther comprises a pivot pin disposed between a first outer bar and asecond outer bar; wherein said pivot pin is seated within said pivot ofsaid blade; and wherein said at least one drive member is connected tosaid notch and configured to oscillate said blade about said pivot pinwhen said at least one drive member is reciprocated by said surgicalsaw.
 16. The surgical system of claim 11, wherein the mass of the othercomponents of said blade assembly does not alter the mass moment ofinertia of said blade assembly.
 17. A method of cutting tissue with asurgical saw including a blade assembly having a static guide bar, ablade at least partially disposed within a distal end of the staticguide bar; and at least one drive member connected having opposed endsconnected to the blade and the surgical saw, said method comprising:actuating the at least one drive member with the surgical saw causingthe blade to be oscillated, such that the blade is the only component ofthe blade assembly that oscillates.
 18. The method of claim 17, furthercomprising the step of removably coupling the blade assembly to a headof the surgical saw.
 19. The method of claim 18, wherein the step ofactuating the at least one drive member comprises alternatinglyreciprocating a first drive member and a second drive member that arecoupled to the blade on opposing sides of a pivot point about which theblade is oscillated.